Assay of urea with p-dimethylaminobenzaldehyde

p-Dimethylaminobenzaldehyde and urea in acid media give yellow colouration. The chromogen responsible for the yellow colour is Schiff base(l). The structure of chromogen is illustrated with chemical and spectroscopic means. The yellow colour absorbs at lambda(max) 420 nm. The fluctuation of yellow colour absorbance depends upon the strength of acid Several mineral acids and their mixtures with different concentrations in methanol have been tried as reaction media, but, the CH3OH-H2SO4 mixture appears to be the best and yield good results. The optimum amount of H2SO4 (36N) 0.2 - 0.3 ml in CH3OH is found to be the best reaction media where reactants and products do not get precipitated In it, the yellow colour remains stable and is used as an analytical tool for the determination of urea present in biological fluids. The % age of urea is calculated using p-dimethylaminobenzaldehyde, diacetylemono-oxime and urease (enzymatic) methods.